1. Field of Invention
The present invention relates to a method of producing benzene phosphinic acid having improved flowability.
2. Description of Related Art
Benzene phosphinic acid (hereinafter sometimes referred to as “BZPA”) is sold in bulk quantities for use in a variety of applications including, for example, as a color stabilizer where hindered phenols are not effective, a modifying agent for use in polyamides, an antioxidant, an intermediate for forming metallic salts used as stabilizers, an accelerator for organic peroxide catalysts, a free radical promoter in emulsion polymerization, an improver of polysiloxane resins, and a corrosion inhibitor on thin aluminum surfaces. BZPA is typically prepared by the hydrolysis of benzene phosphonous dichloride. The resulting aqueous slurry is treated by centrifugation or other filtration means to separate the BZPA particles, which are typically small needle-shape crystals, from the aqueous medium. Upon drying, solid crystals of BZPA are obtained in a powder-like form.
Due to its hygroscopicity and other physical and chemical characteristics, BZPA crystals have a strong tendency to agglomerate. Depending upon various conditions such as the length of time the BZPA crystals are stored, the storage conditions, the storage container shape and size, the temperature and the humidity, the extent of agglomeration may vary from a few lumps or clumps within the powder to a complete solid mass throughout the container. Agglomeration, which is also sometimes described as caking or compaction, renders BZPA difficult to handle, because the material does not flow freely out of the container into which it has been packaged. The agglomeration problem can present a potential safety risk (i.e., back strain) to the individuals who attempt to remove the BZPA from shipping and storage containers.